[cfe-users] CFG that accurately reflects constructor elision

[Ben Liblit via cfe-users]

I am building a standalone tool (based on LibTooling) that needs accurate information about where constructors and implicit destructors are called in C++ code.  Building a CFG with options AddImplicitDtors and AddTemporaryDtors set to true seems like a good strategy for this.  However, that CFG does not reflect removals due to constructor elision: it is identical regardless of whether LangOptions::ElideConstructors is on or off.

For constructors, presumably I can use CXXConstructExpr::isElidable() and assume that all elidable constructor calls will indeed be elided if ElideConstructors is on.  But how do I recognize implicit destructor calls that would also be removed?  Put differently, suppose I have a particular CFGAutomaticObjDtor or CFGTemporaryDtor instance "dtor". Can I find the corresponding CXXConstructExpr "ctor" such that if "ctor" had been elided, then "dtor" would never have been added to the CFG in the first place?

As an alternative, is there a way for my tool to explicitly apply constructor elision *before* building the CFG?  That would seem simplest, if it is possible.  But a look through Clang's code suggests that elision happens on-the-fly during code generation, not as a distinct transformation.

Thanks for any suggestions,
Ben